Surgeon factor on laser in situ keratomileusis in low and moderate myopia
148
Istiantoro and Primadina
Med J Indones
Surgeon factor on Laser In Situ Keratomileusis in low and moderate
myopia
Istiantoro, Nandia Primadina
Abstrak
Penelitian ini bertujuan mengevaluasi efektifitas dan prediktabilitas prosedur Laser in situ Keratomileusis (LASIK) pada miopia
ringan dan miopia sedang, yang dikerjakan oleh tiga pembedah. Bersifat retrospektif, data diambil dari rekam medis 68 penderita
(129 mata) yang menjalani prosedur LASIK. Prosedur LASIK dilakukan oleh 3 pembedah (X, Y dan Z) dengan menggunakan
instrumen dan prosedur pembedahan yang sama. Pasien dikelompokkan menjadi 2 kelompok, yaitu kelompok A (kurang dari S-6.00
dioptri) dan kelompok B (S-6.00 – S-10.00 dioptri). Evaluasi tindak lanjut dilakukan pada hari ke-1, ke-7, bulan ke-1 dan ke-3. Hasil :
Efektifitas dan prediktabilitas dinilai berdasarkan tajam penglihatan tanpa koreksi dan status refraksi (dalam ekuivalen sferis) yang
dicapai. Sebaran korelasi antara koreksi yang diharapkan dan yang diperoleh dihitung dengan menggunakan koefisien determinasi
(R2). Uji statistik menunjukkan hasil yang relatif sama untuk ketiga pembedah. Ternyata efektifitas dan prediktabilitas prosedur
LASIK yang dilakukan oleh tiga pembedah menunjukkan hasil yang relatif sama. Faktor pembedah tampaknya tidak mempengaruhi
hasil prosedur LASIK. (Med J Indones 2003; 12: 148-54)
Abstract
The purpose of this study was to evaluate the effectiveness and predictability of Laser in situ Keratomileusis (LASIK) procedure performed
by three surgeons in low and moderate myopia. One hundred twenty nine eyes from 68 patients underwent LASIK procedure, performed
by three different surgeons (X, Y, Z) using the same procedure and same instruments were reviewed. These patients are divided into two
groups, group A ( below – 6.00 diopters ) and group B ( between – 6.00 and –10.00 diopters ). Patients were observed on day 1, day 7, 1st
month and 3rd month. Results: The evaluation of effectiveness and predictability is based upon uncorrected visual acuity (UCVA) and
spherical equivalent refraction, respectively. The variation dispersion between attempted correction and achieved correction is measured
using coefficient of determination (R2). The statistical analysis shows indifferent results for the three surgeons. The conclusion was that the
effectiveness and predictability of LASIK procedure performed by the three surgeons in both groups are indifferent. Hence, this study suggests
that the surgeon factor does not affect the result of LASIK procedure. (Med J Indones 2003; 12: 148-54)
Keywords: LASIK, spherical equivalent, visual aquity
The rapid development of refractive surgery
technology has been focused on increasing
effectiveness, predictability and stability of the
outcome in order to serve patient satisfaction.1,2 Laser
In Situ Keratomileusis (LASIK) is one of refractive
surgery technique that is believed to be effective, safe,
predictable, giving a fast and stable visual recovery
with minimal post-operative pain.1-4 However, the
technique still requires a significant surgical skill.3,4
The procedure of LASIK encompasses a combination
of creating corneal flap using a microkeratome
Department of Ophthalmology, Faculty of Medicine, University of
Indonesia/Dr. Cipto Mangunkusumo Hospital, Jakarta, Indonesia
followed by refractive photo ablation on stromal bed
with Argon Fluorine Excimer Laser. Corneal flap is
then laid back to protect corneal epithel and Bowman
membrane.3-7 This is aimed at giving a better surgical
outcome i.e. faster wound recovery, minimal subepithelial haze and minimal regression.3,4,6-9
Theoretically, the LASIK standard operating
procedures will give high effectiveness, predictability,
and safety.1,8,9 Nevertheless, due to complex surgical
procedure, the success of LASIK depends on the
instruments as well as the surgeon, who should
possess the skill to operate the instruments, and
cooperation from the patient.3,4,10 Therefore, a
question of whether different surgeons would affect
LASIK results, arises.
Vol 12, No 3, July – September 2003
Surgeon factor on laser in situ keratomileusis
This article presents an evaluation of the effectiveness
and predictability of LASIK procedure performed by
three different surgeons in low and moderate myopia.
METHODS
Patient and Study Design
We retrospectively studied the records of patients who
underwent LASIK for myopia at the Jakarta Eye
Center from January 1, 1998 to December 31, 1998.
The inclusion criteria were 20-30 years of age, more
than 500 micron of central corneal thickness, the
usage of Maria Clara nomogram in LASIK algorithm
program and 160 m of corneal flap thickness. The
patients were excluded from the study if there was
complication during follow up. The eyes of the
patients included in this study, were grouped based on
the amount of preoperative spherical equivalent (SE).
Group A comprised of eyes with SE less than -6.00
diopters (D) and group B with SE between –6.00 and
–10.00 D.
Preoperative Examination
Preoperative examinations comprised of an external,
biomicroscopy and dilated fundus examination. Other
measurements taken were keratometry and pachymetry.
Visual acuity was evaluated without and with
correction using Snellen chart. The result of visual
acuity was converted into Snellen decimal fraction.
Surgical Technique
The LASIK procedure was performed by three
experience surgeons namely X, Y and Z. The three
surgeons performed LASIK procedure with same
technique and instruments. Before performing the
LASIK procedure, the patient’s data were entered into
Chiron 217 Excimer Laser’s computer. The laser
system’s computer program was used to record
parameters such as patient’s identification and ablation
depth, rate and diameter. The LASIK algorithm program
was used with Maria Clara nomogram (Table 1).
Table 1. Maria Clara Nomogram
Spherical Equivalence (D)
Correction added (D)
0.00 to -2.00
-2.50 to -4.00
-4.25 to -6.00
> -6.00
- 0.25
- 0.50
- 0.75
- 1.00
149
The ocular surface was anesthetized with 2%
Lidocaine Hydrochloride at 30, 15 and 5 minutes
before surgery. The eyelids were separated with an
eyelid speculum and the eye cleaned with normal
saline. A landmark was made on the cornea with
gentian violet using a corneal marker. The Automated
Corneal Shaper (ACS) microkeratome (Chiron
Vision) and suction ring were assembled by the
surgeon to make a 160 m corneal flap. Then a
suction ring was applied, centered on the previous
marks. Intraocular pressure (IOP) was verified to be
greater than 65 mmHg with Barraquer tonometer.
The corneal surface was irrigated with Balance Salt
Solution (BSS) and the microkeratome head placed in
position to produce a corneal flap. After the corneal
flap was formed, the microkeratome and suction ring
were removed and the flap was reflected nasally. The
exposed stromal bed must be in the dry condition
before ready for laser ablation.
An ArF excimer laser system (Chiron 217) was used
to correct refractive errors. The excimer laser
produced 193 nm ultraviolet light with a fluence of
160 mJ/cm2 and a pulse rate of 5 Hz. Before ablation,
the patient must fixated the eye to green fixation light.
After excimer laser ablation, the ablated stromal bed
was irrigated with BSS. The corneal bed and the inner
surface of the flap were dried with micro sponges, and
the flap was realigned with the marks to its original
position. Striae test was performed to determine
whether the flap had been properly seated and
forming a good adhesion with stromal bed. At the end
of the surgery, Chloramphenicol 0.5% eye drops were
instilled into that eye and continued to instill three
times daily for 7 days. Eyes were protected with a
clear shield after surgery.
Post-operative Examination
Follow-up examinations were scheduled for day 1,
day 7, the first and third month post ope-ratively. The
examinations included visual acuity without and with
correction.
The result was used to evaluate the effectiveness and
the predictability for each surgeons. Effectiveness is
the best result achieved from LASIK procedure and
measured as uncorrected visual acuity (UCVA).
Predictability is the accuracy of the result compared to
predicted outcome and calculated as refractive
correction in SE.
Istiantoro and Primadina
150
Med J Indones
17 eyes were followed-up at day 1, 16 eyes at day 7,
13 eyes at the first month and 16 eyes at the third month.
RESULTS
Sixty-eight patients (129 eyes) underwent LASIK
procedures for myopia correction between January
1,1998 and December 31,1998.
Surgeon X performed LASIK procedure on 21
patients (30 eyes) and all eyes were included in this
study. From 30 eyes, 13 eyes were put in- group A
and 17 eyes were in-group B. Surgeon Y had LASIK
procedure on 24 patients (49 eyes) and all eyes were
included in this study. Thirty-five eyes were in-group
A and 14 eyes were in-group B. Surgeon Z performed
LASIK procedure on 23 patients (50 eyes) and all
eyes were included in this study. From 50 eyes, 39
were in-group A and 11 were in-group B.
The mean of preoperative UCVA in both groups of
surgeon X was 0.075 + 0.015 and the mean of SE was –
5.778 + 1.88, and the mean of cylinder was –0.73 + 0.69.
For both groups of surgeon Y, the mean of preoperative
UCVA was 0.069 + 0.08, and the mean of SE was –
4.689 + 1.78 and the mean of cylinder was -1.267 +
1.26. Both groups of surgeon Z had preoperative UCVA
mean of 0.076 + 0.07 and SE mean of –4.652 + 1.59 and
cylinder mean of –0.875 + 0.58.
In-group A, follow-up patients from surgeon X were
13 eyes at day 1, 12 eyes at day 7, 11 eyes at the first
month and only 3 eyes at the third month. In-group B,
Of surgeon Y, follow-up patients (group A) at day 1
were 35 eyes, 32 eyes at day 7, 31 eyes at the first month
and 16 eyes at the third month. In-group B, follow-up
was obtained for 14 eyes at day 1, 13 eyes at day 7, 10
eyes at the first month and 8 eyes at the third month.
For surgeon Z’s group A, the follow-up eyes were 39
at day 1, 39 eyes at day 7, 28 eyes at the first month
and 23 eyes at the third month. In-group B, follow-up
was obtained for 11 eyes at day 1, 11 eyes at day 7, 8
eyes at the first month and 3 eyes at the third month.
Table 2 shows refractive data for group A and BIn
both groups, there were tendencies of spherical over
correction, except of surgeon X in-group A which the
tendency becoming myopic after 3rd month. However,
the spherical equivalent over-correction in both
groups for all surgeons was less than 1.00 D.
In table 3, it can be seen that surgeon X has 100% of
UCVA > 0.5, and for surgeon Z, it was achieved at 1st
and 3rd month follow-up, while for surgeon Y, the
100% of UCVA > 0.5 was reached at 3rd month.
In-group B, 100% of UCVA > 0.5 was achieved by
surgeon Y and Z at 1st and 3rd month follow-up, while
for surgeon X, by 3rd month the percentage was only at
87.50%.
Table 2. Refractive results for Group A and B
Surgeon
Follow-up
schedule
Group A
Group B
Number of
Eyes
UCVA
Mean + SD
Spher. Eq.
Mean + SD
Number of
Eyes
UCVA
Mean + SD
Spher. Eq.
Mean + SD
X
Pre-op
Day 1
Day 7
1st month
3rd month
13
13
12
11
3
0.113 + 0.15
0.862 + 0.13
0.900 + 0.11
0.936 + 0.12
0.867 + 0.23
-4.125 + 1.28
0.346 + 0.46
0.229 + 0.36
0.182 + 0.25
-0.125 + 0.22
17
17
16
13
16
0.047 + 0.02
0.565 + 0.24
0.631 + 0.28
0.754 + 0.19
0.744 + 0.22
-7.051 + 1.12
0.838 + 0.89
0.539 + 0.63
0.481 + 0.68
0.273 + 0.57
Y
Pre-op
Day 1
Day 7
1st month
3rd month
35
35
32
31
16
0.081 + 0.09
0.803 + 0.20
0.834 + 0.20
0.839 + 0.21
0.863 + 0.17
-3.821 + 1.21
0.296 + 0.57
0.191 + 0.43
0.190 + 0.38
0.094 + 0.25
14
14
13
10
8
0.042 + 0.01
0.714 + 0.28
0.769 + 0.29
0.88 + 0.17
0.9 + 0.09
-6.857 + 0.92
0.830 + 0.82
0.471 + 0.82
0.15 + 0.32
0.109 + 0.18
Z
Pre-op
Day 1
Day 7
1st month
3rd month
39
39
39
28
23
0.087 + 0.08
0.799 + 0.18
0.887 + 0.16
0.939 + 0.09
0.951 + 0.09
-4.019 + 1.14
0.516 + 0.59
0.202 + 0.36
0.022 + 0.17
0.027 + 0.18
11
11
11
8
3
0.038 + 0.02
0.718 + 0.29
0.827 + 0.25
0.962 + 0.05
1.00 + 0.00
-6.898 + 0.70
0.750 + 0.66
0.318 + 0.46
0.125 + 0.23
0.083 + 0.14
Vol 12, No 3, July – September 2003
Surgeon factor on laser in situ keratomileusis
It can be seen from the scatter plot below, that there is
a tendency of over correction with coefficient of
determinant (R2) of 0.9577.
This tendency can also be seen in figure 2 (for
surgeon Y) and figure 3 (for surgeon Z) where the
coefficients of determinants (R2) were 0.939 and
0.9723 respectively.
Table 3. Uncorrected Visual Acuity (UCVA) results (%)
X
Y
Z
Group A
1st day
7th day
1st mth
3rd mth
> 0.8
< 0.8
> 0.5
84.62 %
83.33 %
81.82 %
66.67 %
15.38 %
16.67 %
18.18 %
33.33 %
< 0.5
0%
0%
0%
0%
> 0.8
< 0.8
> 0.5
< 0.5
74.29 %
68.75 %
70.97 %
87.50 %
17.14 %
28.13 %
19.35 %
12.50 %
8.57 %
3.13 %
9.68 %
0%
X
> 0.8
< 0.8
> 0.5
< 0.5
66.67 %
79.49 %
92.86 %
95.65 %
28.20 %
17.95 %
7.14 %
4.35 %
5.13 %
2.56 %
0%
0%
Y
Z
Group B
1st day
7th day
1st mth
3rd mth
> 0.8
< 0.8
> 0.5
23.53 %
37.50 %
69.23 %
56.25 %
47.06 %
43.75 %
23.08 %
31.25 %
< 0.5
29.41 %
18.75 %
7.69 %
12.50 %
> 0.8
< 0.8
> 0.5
< 0.5
50.00 %
69.23 %
80.00 %
87.50 %
35.71 %
15.38 %
20.00 %
12.50 %
14.29 %
15.38 %
0%
0%
12
12
10
10
achieved (D)
achieved (D)
8
R2 = 0,9577
6
4
> 0.8
< 0.8
> 0.5
< 0.5
63.63 %
72.73 %
100 %
100 %
18.08 %
18.08 %
0%
0%
18.08 %
9.09 %
0%
0%
R2 = 0,939
8
6
4
2
2
0
0
0
2
4
6
8
10
12
151
0
2
attempted (D)
Figure 1. Scattered plot of attempted vs. achieved correction at 3 rd month (surgeon X)
Figure 2. Scattered plot of attempted vs. achieved correction at 3rd month (surgeon Y)
4
6
attempted (D)
8
10
12
Istiantoro and Primadina
152
Med J Indones
On the other hand, in-group B, 100% predictability
within + 0.5 D was achieved by surgeon Y and Z,
while surgeon X had only the predictability of
68.75%. (Figure 5)
10
achi eved (D)
8
6
4
DISCUSSION
2
0
0
2
4
6
8
10
attempted (D)
Figure 3. Scattered plot of attempted vs. achieved correction at 3rd
month (surgeon Z)
70
60
50
40
X
30
Y
Z
20
10
0
-1.0
- 0.5
0
0.5
1.0
1.5
Figure 4. Spherical equivalent refractive outcome in-group A
at 3rd month follow-up
Figure 4 shows that the predictability measured by
spherical equivalent outcome for surgeon X and Z
were 100% within + 0.5 D. Whilst by surgeon Y,
93.75% predictability were within + 0.5 D.
Presently, LASIK technique is believed as a corneal
refractive surgery with high effectiveness, high
predictability and good refraction stability.1,8,9
Nevertheless, the satis-fied result can only be attained
if the patient, surgeon and instruments are well
prepared.3,4 The LASIK technique is not fully
dependent on the instruments, but it needs experienced
surgeon and cooperation from the patient.10
This study reveals that the result of UCVA > 0.5 ingroup A was 100% achieved by surgeon X and Z at
1st and 3rd month follow-up, while surgeon Y was
reached the same percentage at 3rd month follow-up.
In-group B, UCVA > 0.5 was 100% achieved by
surgeon Y and Z at 1st and 3rd month follow-up. The
achievement of surgeon X was less than of the two
surgeons, i.e. 92.31% at 1st month follow-up and
87.50% at 3rd month follow-up.
Maldonado et al11 reported the UCVA > 0.5 in
myopia between –3.00 D and –6.00 D was 96.43%,
while for myopia between –6.25 D and –10.00 D was
76.64%. Knorz et al12 also found the UCVA > 0.5 in
myopia between –5.00 D and –9.90 D was 71 to
88%, and for myopia between –10.00 D and –14.90
D was decreased to 33%. The study of Salchow et al7
describe that the UCVA > 0.5 for myopia between –
1.50 D and –16.00 D is 82.50%.
This study suggests a similar outcome to those
previous study. For certain result, this study is even
better than the previous study. The UCVA > 0.5 was
achieved 100% by surgeon X,Y and Z in-group A and
by surgeon Y and Z in-group B.
80
70
60
50
X
40
Y
30
Z
20
10
0
- 0.5
0
0.5
1.0
Figure 5. Spherical equivalent refractive outcome in-group B
at 3rd month follow-up
Predictability in-group A was 100% within +1.00 D
at 1st and 3rd month follow-up for all surgeons. In fact,
predictability for surgeon X and Z were 100% within
+0.5 D, while for surgeon Y is less than of the two
surgeons, i.e. 90.42%. In-group B, the predictability
is less than group A for all surgeons. Surgeon Y and
Z have predictability of 100% within +1.00 D, and for
surgeon X the percentage is 89.19%.
Vol 12, No 3, July – September 2003
Salchow et al7 reported that predictability for myopia
between –1.50 D and –16.00 D was 81% within +1.00
D. On the other hand, Maldonado et al11 reported that
predictability for myopia between –3.00 D and –6.00
D was 82.14% within +1.00 D, but the result was
decreased to 58.70% for myopia between –6.25 D and
–10.00 D. The predictability in this study seems better
than of Maldonado, i.e. 89.19-100% within + 1.00 D.
The result of this study is also indifferent with of
Knorz et al7. The predictability is 100% within + 1.00
D for low and moderate myopia, but for high myopia
(more than -15.00 D) the predictability is decreased to
38.9%.
This study shows high effectiveness and predictability
for all surgeons in low and moderate myopia, although
the outcome is not exactly the same. The effectiveness
and predictability for surgeon Z is good in both low and
moderate myopia, while surgeon Y is good in moderate
myopia and surgeon X is in low myopia. Based on the
scatter diagrams of attempted correction versus
achieved correction, all three surgeons come up with
high coefficients of determinant between 0.93 to 0.97.
This implies that the three surgeons have similar
results.
Several factors can influence the effectiveness and
predictability of LASIK procedure namely the
instruments, the surgeon and the patient.3,4
The excimer laser machine has a specific ablation
homogenecity which can influence the accuracy of
LASIK procedure’s result, since it produces the
clinical profile which determine the predictabiliy and
refraction stability, also the complication possibility
such as central islands.3
In this study, all of the surgeons use the same excimer
laser machine, so the different result among surgeons
is not because of the machine. However, the different
result can be caused by different estimation when the
surgeons performing ablation laser beam test.3,4
The excimer laser computer algorithm calculates the
amount of ablation based on corneal thickness,
ablation diamater and spherical correction using
normogram in order to obtain the correction result as
predicted. The use of normogram is aimed at minimizing
undercorrection as well as overcorrection.3,4,13
Since all surgeons in this study use same Maria Clara
normogram, so there will be no different of amount
correction calculated by the machine.
Surgeon factor on laser in situ keratomileusis
153
The laser machine and microkeratome are automated.
Once the microkeratome begins to progress the cornea
and the excimer laser begins its ablation, the surgeon
does not have control over the instrument.13 Therefore,
the instrument preparation such as microkeratome
assembling and examination, and ablation laser beam
test must be prepared well before the surgery.3,4,13
For those reasons, the surgeon skill in performing and
authorizing LASIK’s instrument is absolutely needed
in order to obtain a satisfied result.13
The surgeon, for example, has to put the suction ring
on the central cornea to make a good flap which will
give a good focus and centration of ablation.3,4
On the other hand, hydration level when the
automated corneal shaper (ACS) moving can
influence the accuracy of LASIK procedure. Wet
surface of the cornea can break the microkeratome’s
motor and this will influence the progress of
microkeratome on corneal surface. Stromal hydration
level in ablation progress can also influence the result
of LASIK procedure. Wet corneal surface can
interfere the laser beam, which increase the risk of
overcorrection and central islands.3,4
The effectiveness and predictability are also
dependent to cooperation between patient and
surgeon. Eye movement and poor fixation while the
ablation progressing can influence the refraction
result.3,4 The patient must fixate the eye to green light
fixation to avoid ablation decentration. However, in
this study the surgeons use the eye tracker to avoid the
decentration.14,15
Hence, different effectiveness and predictability of the
results might be caused by surgeon factor as explained
before.
This study, however shows that effectiveness and
predictability by three surgeons performed LASIK
procedure using the same procedure and instruments
are indifferent. In conclusion, its seem that the
surgeon factor does not affect the LASIK results.
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Vol 12, No 3, July – September 2003
Surgeon factor on laser in situ keratomileusis
155
Istiantoro and Primadina
Med J Indones
Surgeon factor on Laser In Situ Keratomileusis in low and moderate
myopia
Istiantoro, Nandia Primadina
Abstrak
Penelitian ini bertujuan mengevaluasi efektifitas dan prediktabilitas prosedur Laser in situ Keratomileusis (LASIK) pada miopia
ringan dan miopia sedang, yang dikerjakan oleh tiga pembedah. Bersifat retrospektif, data diambil dari rekam medis 68 penderita
(129 mata) yang menjalani prosedur LASIK. Prosedur LASIK dilakukan oleh 3 pembedah (X, Y dan Z) dengan menggunakan
instrumen dan prosedur pembedahan yang sama. Pasien dikelompokkan menjadi 2 kelompok, yaitu kelompok A (kurang dari S-6.00
dioptri) dan kelompok B (S-6.00 – S-10.00 dioptri). Evaluasi tindak lanjut dilakukan pada hari ke-1, ke-7, bulan ke-1 dan ke-3. Hasil :
Efektifitas dan prediktabilitas dinilai berdasarkan tajam penglihatan tanpa koreksi dan status refraksi (dalam ekuivalen sferis) yang
dicapai. Sebaran korelasi antara koreksi yang diharapkan dan yang diperoleh dihitung dengan menggunakan koefisien determinasi
(R2). Uji statistik menunjukkan hasil yang relatif sama untuk ketiga pembedah. Ternyata efektifitas dan prediktabilitas prosedur
LASIK yang dilakukan oleh tiga pembedah menunjukkan hasil yang relatif sama. Faktor pembedah tampaknya tidak mempengaruhi
hasil prosedur LASIK. (Med J Indones 2003; 12: 148-54)
Abstract
The purpose of this study was to evaluate the effectiveness and predictability of Laser in situ Keratomileusis (LASIK) procedure performed
by three surgeons in low and moderate myopia. One hundred twenty nine eyes from 68 patients underwent LASIK procedure, performed
by three different surgeons (X, Y, Z) using the same procedure and same instruments were reviewed. These patients are divided into two
groups, group A ( below – 6.00 diopters ) and group B ( between – 6.00 and –10.00 diopters ). Patients were observed on day 1, day 7, 1st
month and 3rd month. Results: The evaluation of effectiveness and predictability is based upon uncorrected visual acuity (UCVA) and
spherical equivalent refraction, respectively. The variation dispersion between attempted correction and achieved correction is measured
using coefficient of determination (R2). The statistical analysis shows indifferent results for the three surgeons. The conclusion was that the
effectiveness and predictability of LASIK procedure performed by the three surgeons in both groups are indifferent. Hence, this study suggests
that the surgeon factor does not affect the result of LASIK procedure. (Med J Indones 2003; 12: 148-54)
Keywords: LASIK, spherical equivalent, visual aquity
The rapid development of refractive surgery
technology has been focused on increasing
effectiveness, predictability and stability of the
outcome in order to serve patient satisfaction.1,2 Laser
In Situ Keratomileusis (LASIK) is one of refractive
surgery technique that is believed to be effective, safe,
predictable, giving a fast and stable visual recovery
with minimal post-operative pain.1-4 However, the
technique still requires a significant surgical skill.3,4
The procedure of LASIK encompasses a combination
of creating corneal flap using a microkeratome
Department of Ophthalmology, Faculty of Medicine, University of
Indonesia/Dr. Cipto Mangunkusumo Hospital, Jakarta, Indonesia
followed by refractive photo ablation on stromal bed
with Argon Fluorine Excimer Laser. Corneal flap is
then laid back to protect corneal epithel and Bowman
membrane.3-7 This is aimed at giving a better surgical
outcome i.e. faster wound recovery, minimal subepithelial haze and minimal regression.3,4,6-9
Theoretically, the LASIK standard operating
procedures will give high effectiveness, predictability,
and safety.1,8,9 Nevertheless, due to complex surgical
procedure, the success of LASIK depends on the
instruments as well as the surgeon, who should
possess the skill to operate the instruments, and
cooperation from the patient.3,4,10 Therefore, a
question of whether different surgeons would affect
LASIK results, arises.
Vol 12, No 3, July – September 2003
Surgeon factor on laser in situ keratomileusis
This article presents an evaluation of the effectiveness
and predictability of LASIK procedure performed by
three different surgeons in low and moderate myopia.
METHODS
Patient and Study Design
We retrospectively studied the records of patients who
underwent LASIK for myopia at the Jakarta Eye
Center from January 1, 1998 to December 31, 1998.
The inclusion criteria were 20-30 years of age, more
than 500 micron of central corneal thickness, the
usage of Maria Clara nomogram in LASIK algorithm
program and 160 m of corneal flap thickness. The
patients were excluded from the study if there was
complication during follow up. The eyes of the
patients included in this study, were grouped based on
the amount of preoperative spherical equivalent (SE).
Group A comprised of eyes with SE less than -6.00
diopters (D) and group B with SE between –6.00 and
–10.00 D.
Preoperative Examination
Preoperative examinations comprised of an external,
biomicroscopy and dilated fundus examination. Other
measurements taken were keratometry and pachymetry.
Visual acuity was evaluated without and with
correction using Snellen chart. The result of visual
acuity was converted into Snellen decimal fraction.
Surgical Technique
The LASIK procedure was performed by three
experience surgeons namely X, Y and Z. The three
surgeons performed LASIK procedure with same
technique and instruments. Before performing the
LASIK procedure, the patient’s data were entered into
Chiron 217 Excimer Laser’s computer. The laser
system’s computer program was used to record
parameters such as patient’s identification and ablation
depth, rate and diameter. The LASIK algorithm program
was used with Maria Clara nomogram (Table 1).
Table 1. Maria Clara Nomogram
Spherical Equivalence (D)
Correction added (D)
0.00 to -2.00
-2.50 to -4.00
-4.25 to -6.00
> -6.00
- 0.25
- 0.50
- 0.75
- 1.00
149
The ocular surface was anesthetized with 2%
Lidocaine Hydrochloride at 30, 15 and 5 minutes
before surgery. The eyelids were separated with an
eyelid speculum and the eye cleaned with normal
saline. A landmark was made on the cornea with
gentian violet using a corneal marker. The Automated
Corneal Shaper (ACS) microkeratome (Chiron
Vision) and suction ring were assembled by the
surgeon to make a 160 m corneal flap. Then a
suction ring was applied, centered on the previous
marks. Intraocular pressure (IOP) was verified to be
greater than 65 mmHg with Barraquer tonometer.
The corneal surface was irrigated with Balance Salt
Solution (BSS) and the microkeratome head placed in
position to produce a corneal flap. After the corneal
flap was formed, the microkeratome and suction ring
were removed and the flap was reflected nasally. The
exposed stromal bed must be in the dry condition
before ready for laser ablation.
An ArF excimer laser system (Chiron 217) was used
to correct refractive errors. The excimer laser
produced 193 nm ultraviolet light with a fluence of
160 mJ/cm2 and a pulse rate of 5 Hz. Before ablation,
the patient must fixated the eye to green fixation light.
After excimer laser ablation, the ablated stromal bed
was irrigated with BSS. The corneal bed and the inner
surface of the flap were dried with micro sponges, and
the flap was realigned with the marks to its original
position. Striae test was performed to determine
whether the flap had been properly seated and
forming a good adhesion with stromal bed. At the end
of the surgery, Chloramphenicol 0.5% eye drops were
instilled into that eye and continued to instill three
times daily for 7 days. Eyes were protected with a
clear shield after surgery.
Post-operative Examination
Follow-up examinations were scheduled for day 1,
day 7, the first and third month post ope-ratively. The
examinations included visual acuity without and with
correction.
The result was used to evaluate the effectiveness and
the predictability for each surgeons. Effectiveness is
the best result achieved from LASIK procedure and
measured as uncorrected visual acuity (UCVA).
Predictability is the accuracy of the result compared to
predicted outcome and calculated as refractive
correction in SE.
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150
Med J Indones
17 eyes were followed-up at day 1, 16 eyes at day 7,
13 eyes at the first month and 16 eyes at the third month.
RESULTS
Sixty-eight patients (129 eyes) underwent LASIK
procedures for myopia correction between January
1,1998 and December 31,1998.
Surgeon X performed LASIK procedure on 21
patients (30 eyes) and all eyes were included in this
study. From 30 eyes, 13 eyes were put in- group A
and 17 eyes were in-group B. Surgeon Y had LASIK
procedure on 24 patients (49 eyes) and all eyes were
included in this study. Thirty-five eyes were in-group
A and 14 eyes were in-group B. Surgeon Z performed
LASIK procedure on 23 patients (50 eyes) and all
eyes were included in this study. From 50 eyes, 39
were in-group A and 11 were in-group B.
The mean of preoperative UCVA in both groups of
surgeon X was 0.075 + 0.015 and the mean of SE was –
5.778 + 1.88, and the mean of cylinder was –0.73 + 0.69.
For both groups of surgeon Y, the mean of preoperative
UCVA was 0.069 + 0.08, and the mean of SE was –
4.689 + 1.78 and the mean of cylinder was -1.267 +
1.26. Both groups of surgeon Z had preoperative UCVA
mean of 0.076 + 0.07 and SE mean of –4.652 + 1.59 and
cylinder mean of –0.875 + 0.58.
In-group A, follow-up patients from surgeon X were
13 eyes at day 1, 12 eyes at day 7, 11 eyes at the first
month and only 3 eyes at the third month. In-group B,
Of surgeon Y, follow-up patients (group A) at day 1
were 35 eyes, 32 eyes at day 7, 31 eyes at the first month
and 16 eyes at the third month. In-group B, follow-up
was obtained for 14 eyes at day 1, 13 eyes at day 7, 10
eyes at the first month and 8 eyes at the third month.
For surgeon Z’s group A, the follow-up eyes were 39
at day 1, 39 eyes at day 7, 28 eyes at the first month
and 23 eyes at the third month. In-group B, follow-up
was obtained for 11 eyes at day 1, 11 eyes at day 7, 8
eyes at the first month and 3 eyes at the third month.
Table 2 shows refractive data for group A and BIn
both groups, there were tendencies of spherical over
correction, except of surgeon X in-group A which the
tendency becoming myopic after 3rd month. However,
the spherical equivalent over-correction in both
groups for all surgeons was less than 1.00 D.
In table 3, it can be seen that surgeon X has 100% of
UCVA > 0.5, and for surgeon Z, it was achieved at 1st
and 3rd month follow-up, while for surgeon Y, the
100% of UCVA > 0.5 was reached at 3rd month.
In-group B, 100% of UCVA > 0.5 was achieved by
surgeon Y and Z at 1st and 3rd month follow-up, while
for surgeon X, by 3rd month the percentage was only at
87.50%.
Table 2. Refractive results for Group A and B
Surgeon
Follow-up
schedule
Group A
Group B
Number of
Eyes
UCVA
Mean + SD
Spher. Eq.
Mean + SD
Number of
Eyes
UCVA
Mean + SD
Spher. Eq.
Mean + SD
X
Pre-op
Day 1
Day 7
1st month
3rd month
13
13
12
11
3
0.113 + 0.15
0.862 + 0.13
0.900 + 0.11
0.936 + 0.12
0.867 + 0.23
-4.125 + 1.28
0.346 + 0.46
0.229 + 0.36
0.182 + 0.25
-0.125 + 0.22
17
17
16
13
16
0.047 + 0.02
0.565 + 0.24
0.631 + 0.28
0.754 + 0.19
0.744 + 0.22
-7.051 + 1.12
0.838 + 0.89
0.539 + 0.63
0.481 + 0.68
0.273 + 0.57
Y
Pre-op
Day 1
Day 7
1st month
3rd month
35
35
32
31
16
0.081 + 0.09
0.803 + 0.20
0.834 + 0.20
0.839 + 0.21
0.863 + 0.17
-3.821 + 1.21
0.296 + 0.57
0.191 + 0.43
0.190 + 0.38
0.094 + 0.25
14
14
13
10
8
0.042 + 0.01
0.714 + 0.28
0.769 + 0.29
0.88 + 0.17
0.9 + 0.09
-6.857 + 0.92
0.830 + 0.82
0.471 + 0.82
0.15 + 0.32
0.109 + 0.18
Z
Pre-op
Day 1
Day 7
1st month
3rd month
39
39
39
28
23
0.087 + 0.08
0.799 + 0.18
0.887 + 0.16
0.939 + 0.09
0.951 + 0.09
-4.019 + 1.14
0.516 + 0.59
0.202 + 0.36
0.022 + 0.17
0.027 + 0.18
11
11
11
8
3
0.038 + 0.02
0.718 + 0.29
0.827 + 0.25
0.962 + 0.05
1.00 + 0.00
-6.898 + 0.70
0.750 + 0.66
0.318 + 0.46
0.125 + 0.23
0.083 + 0.14
Vol 12, No 3, July – September 2003
Surgeon factor on laser in situ keratomileusis
It can be seen from the scatter plot below, that there is
a tendency of over correction with coefficient of
determinant (R2) of 0.9577.
This tendency can also be seen in figure 2 (for
surgeon Y) and figure 3 (for surgeon Z) where the
coefficients of determinants (R2) were 0.939 and
0.9723 respectively.
Table 3. Uncorrected Visual Acuity (UCVA) results (%)
X
Y
Z
Group A
1st day
7th day
1st mth
3rd mth
> 0.8
< 0.8
> 0.5
84.62 %
83.33 %
81.82 %
66.67 %
15.38 %
16.67 %
18.18 %
33.33 %
< 0.5
0%
0%
0%
0%
> 0.8
< 0.8
> 0.5
< 0.5
74.29 %
68.75 %
70.97 %
87.50 %
17.14 %
28.13 %
19.35 %
12.50 %
8.57 %
3.13 %
9.68 %
0%
X
> 0.8
< 0.8
> 0.5
< 0.5
66.67 %
79.49 %
92.86 %
95.65 %
28.20 %
17.95 %
7.14 %
4.35 %
5.13 %
2.56 %
0%
0%
Y
Z
Group B
1st day
7th day
1st mth
3rd mth
> 0.8
< 0.8
> 0.5
23.53 %
37.50 %
69.23 %
56.25 %
47.06 %
43.75 %
23.08 %
31.25 %
< 0.5
29.41 %
18.75 %
7.69 %
12.50 %
> 0.8
< 0.8
> 0.5
< 0.5
50.00 %
69.23 %
80.00 %
87.50 %
35.71 %
15.38 %
20.00 %
12.50 %
14.29 %
15.38 %
0%
0%
12
12
10
10
achieved (D)
achieved (D)
8
R2 = 0,9577
6
4
> 0.8
< 0.8
> 0.5
< 0.5
63.63 %
72.73 %
100 %
100 %
18.08 %
18.08 %
0%
0%
18.08 %
9.09 %
0%
0%
R2 = 0,939
8
6
4
2
2
0
0
0
2
4
6
8
10
12
151
0
2
attempted (D)
Figure 1. Scattered plot of attempted vs. achieved correction at 3 rd month (surgeon X)
Figure 2. Scattered plot of attempted vs. achieved correction at 3rd month (surgeon Y)
4
6
attempted (D)
8
10
12
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Med J Indones
On the other hand, in-group B, 100% predictability
within + 0.5 D was achieved by surgeon Y and Z,
while surgeon X had only the predictability of
68.75%. (Figure 5)
10
achi eved (D)
8
6
4
DISCUSSION
2
0
0
2
4
6
8
10
attempted (D)
Figure 3. Scattered plot of attempted vs. achieved correction at 3rd
month (surgeon Z)
70
60
50
40
X
30
Y
Z
20
10
0
-1.0
- 0.5
0
0.5
1.0
1.5
Figure 4. Spherical equivalent refractive outcome in-group A
at 3rd month follow-up
Figure 4 shows that the predictability measured by
spherical equivalent outcome for surgeon X and Z
were 100% within + 0.5 D. Whilst by surgeon Y,
93.75% predictability were within + 0.5 D.
Presently, LASIK technique is believed as a corneal
refractive surgery with high effectiveness, high
predictability and good refraction stability.1,8,9
Nevertheless, the satis-fied result can only be attained
if the patient, surgeon and instruments are well
prepared.3,4 The LASIK technique is not fully
dependent on the instruments, but it needs experienced
surgeon and cooperation from the patient.10
This study reveals that the result of UCVA > 0.5 ingroup A was 100% achieved by surgeon X and Z at
1st and 3rd month follow-up, while surgeon Y was
reached the same percentage at 3rd month follow-up.
In-group B, UCVA > 0.5 was 100% achieved by
surgeon Y and Z at 1st and 3rd month follow-up. The
achievement of surgeon X was less than of the two
surgeons, i.e. 92.31% at 1st month follow-up and
87.50% at 3rd month follow-up.
Maldonado et al11 reported the UCVA > 0.5 in
myopia between –3.00 D and –6.00 D was 96.43%,
while for myopia between –6.25 D and –10.00 D was
76.64%. Knorz et al12 also found the UCVA > 0.5 in
myopia between –5.00 D and –9.90 D was 71 to
88%, and for myopia between –10.00 D and –14.90
D was decreased to 33%. The study of Salchow et al7
describe that the UCVA > 0.5 for myopia between –
1.50 D and –16.00 D is 82.50%.
This study suggests a similar outcome to those
previous study. For certain result, this study is even
better than the previous study. The UCVA > 0.5 was
achieved 100% by surgeon X,Y and Z in-group A and
by surgeon Y and Z in-group B.
80
70
60
50
X
40
Y
30
Z
20
10
0
- 0.5
0
0.5
1.0
Figure 5. Spherical equivalent refractive outcome in-group B
at 3rd month follow-up
Predictability in-group A was 100% within +1.00 D
at 1st and 3rd month follow-up for all surgeons. In fact,
predictability for surgeon X and Z were 100% within
+0.5 D, while for surgeon Y is less than of the two
surgeons, i.e. 90.42%. In-group B, the predictability
is less than group A for all surgeons. Surgeon Y and
Z have predictability of 100% within +1.00 D, and for
surgeon X the percentage is 89.19%.
Vol 12, No 3, July – September 2003
Salchow et al7 reported that predictability for myopia
between –1.50 D and –16.00 D was 81% within +1.00
D. On the other hand, Maldonado et al11 reported that
predictability for myopia between –3.00 D and –6.00
D was 82.14% within +1.00 D, but the result was
decreased to 58.70% for myopia between –6.25 D and
–10.00 D. The predictability in this study seems better
than of Maldonado, i.e. 89.19-100% within + 1.00 D.
The result of this study is also indifferent with of
Knorz et al7. The predictability is 100% within + 1.00
D for low and moderate myopia, but for high myopia
(more than -15.00 D) the predictability is decreased to
38.9%.
This study shows high effectiveness and predictability
for all surgeons in low and moderate myopia, although
the outcome is not exactly the same. The effectiveness
and predictability for surgeon Z is good in both low and
moderate myopia, while surgeon Y is good in moderate
myopia and surgeon X is in low myopia. Based on the
scatter diagrams of attempted correction versus
achieved correction, all three surgeons come up with
high coefficients of determinant between 0.93 to 0.97.
This implies that the three surgeons have similar
results.
Several factors can influence the effectiveness and
predictability of LASIK procedure namely the
instruments, the surgeon and the patient.3,4
The excimer laser machine has a specific ablation
homogenecity which can influence the accuracy of
LASIK procedure’s result, since it produces the
clinical profile which determine the predictabiliy and
refraction stability, also the complication possibility
such as central islands.3
In this study, all of the surgeons use the same excimer
laser machine, so the different result among surgeons
is not because of the machine. However, the different
result can be caused by different estimation when the
surgeons performing ablation laser beam test.3,4
The excimer laser computer algorithm calculates the
amount of ablation based on corneal thickness,
ablation diamater and spherical correction using
normogram in order to obtain the correction result as
predicted. The use of normogram is aimed at minimizing
undercorrection as well as overcorrection.3,4,13
Since all surgeons in this study use same Maria Clara
normogram, so there will be no different of amount
correction calculated by the machine.
Surgeon factor on laser in situ keratomileusis
153
The laser machine and microkeratome are automated.
Once the microkeratome begins to progress the cornea
and the excimer laser begins its ablation, the surgeon
does not have control over the instrument.13 Therefore,
the instrument preparation such as microkeratome
assembling and examination, and ablation laser beam
test must be prepared well before the surgery.3,4,13
For those reasons, the surgeon skill in performing and
authorizing LASIK’s instrument is absolutely needed
in order to obtain a satisfied result.13
The surgeon, for example, has to put the suction ring
on the central cornea to make a good flap which will
give a good focus and centration of ablation.3,4
On the other hand, hydration level when the
automated corneal shaper (ACS) moving can
influence the accuracy of LASIK procedure. Wet
surface of the cornea can break the microkeratome’s
motor and this will influence the progress of
microkeratome on corneal surface. Stromal hydration
level in ablation progress can also influence the result
of LASIK procedure. Wet corneal surface can
interfere the laser beam, which increase the risk of
overcorrection and central islands.3,4
The effectiveness and predictability are also
dependent to cooperation between patient and
surgeon. Eye movement and poor fixation while the
ablation progressing can influence the refraction
result.3,4 The patient must fixate the eye to green light
fixation to avoid ablation decentration. However, in
this study the surgeons use the eye tracker to avoid the
decentration.14,15
Hence, different effectiveness and predictability of the
results might be caused by surgeon factor as explained
before.
This study, however shows that effectiveness and
predictability by three surgeons performed LASIK
procedure using the same procedure and instruments
are indifferent. In conclusion, its seem that the
surgeon factor does not affect the LASIK results.
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